In every case :
Check for the size, and show a message warning if it is too big for an email
Get rid of the main window and launch directly the email writing window, if set in main window app
Evaluate the size of the attachment
Support for Evolution, Thunderbird, Icedove, and Kmail.
Save results in a folder : can be use to resize several pictures and save somewhere
Store settings

Installation:
If your distribution is debian type, use the deb file and the package manager of your distribution
For another cases, use the tar archive and run the "install.sh" script as root in a shell.As for all nautilus extensions, you need to restart your session or the nautilus process to have the mailpictures item in the nautilus edit menu

Locales:
English
French
Italian
German
DutchNote : I'm looking for translators, please leave a comment here to contribute